[nix] ask dune to output errors also at the end of the log

on longer log (i.e. frama-c or plug-in compilation), it can be quite
tedious to check the log in the CI to spot the error. The new option
will instruct dune to put the error message (and its associated
command line) at the end of the log as well.

nix/api-doc.nix

@@ -19,7 +19,7 @@ stdenv.mkDerivation rec {
   ];
 
   buildPhase = ''
-    dune build -j1 @doc
+    dune build -j1 --error-reporting=twice @doc
     cp -r _build/default/_doc/_html frama-c-api
     echo ".dummy" > excluded
     tar czf frama-c-api.tar.gz -X excluded frama-c-api

nix/frama-c.nix

@@ -110,7 +110,7 @@ stdenvNoCC.mkDerivation rec {
   dune_opt = if release_mode then "--release" else "" ;
 
   buildPhase = ''
-    dune build -j2 --display short $release_mode @install
+    dune build -j2 --display short --error-reporting=twice $release_mode @install
     make tools/ptests/ptests.exe
     make tools/ptests/wtests.exe
   '';

nix/internal-tests.nix

@@ -115,7 +115,7 @@ stdenvNoCC.mkDerivation rec {
   # Do not use default parallel building, but allow 2 cores for Frama-C build
   enableParallelBuilding = false;
   buildPhase = ''
-    dune build -j2 --display short @install
+    dune build -j2 --display short --error-reporting=twice @install
     make tools/ptests/ptests.exe
     make tools/ptests/wtests.exe
   '';

nix/mk_plugin.nix

@@ -83,7 +83,7 @@ stdenv.mkDerivation {
   '';
   buildPhase = ''
     runHook preBuild
-    dune build -j2 --display short @install
+    dune build -j2 --display short --error-reporting=twice @install
   '';
 
   wp_cache =